Electrochemical reduction device and method of manufacturing hydride of aromatic hydrocarbon compound or nitrogen-containing heterocyclic aromatic compound

ABSTRACT

An electrochemical reduction device is provided with an electrolyte membrane, an electrode unit, a power control unit, hydrogen gas generation amount measuring unit, and a control unit. The electrolyte membrane has ion conductivity. The electrode unit includes both a reduction electrode that is provided on one side of the electrolyte membrane and contains a reduction catalyst for hydrogenating at least one benzene ring of an aromatic hydrocarbon compound or a nitrogen-containing heterocyclic aromatic compound, and an oxygen evolving electrode. The control unit releases, when the hydrogen gas generation amount F1 is larger than an acceptable upper limit F0 of a hydrogen gas generation amount in the electrode unit, the application of a voltage by the power control unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2012-149794, filed on Jul. 3,2012 and International Patent Application No. PCT/JP2013/004069, filedon Jul. 1, 2013, the entire content of each of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device and a method ofelectrochemically hydrogenating either an aromatic hydrocarbon compoundor a nitrogen-containing heterocyclic aromatic compound.

2. Description of the Related Art

It is known that a cyclic organic compound such as cyclohexane ordecalin can be efficiently obtained by hydrogenating at least onebenzene ring of a corresponding aromatic hydrocarbon compound (benzeneor naphthalene) with the use of hydrogen gas. This reaction requiresreaction conditions of high temperature and high pressure, and hence itis not suitable for small and medium scale manufacturing of cyclicorganic compounds. It is also known that, on the other hand, anelectrochemical reaction using an electrolysis cell proceeds withoutgaseous hydrogen being required and under relatively mild reactionconditions (from normal temperature to approximately 200° C. and normalpressure) because water can be used as a hydrogen source.

SUMMARY OF THE INVENTION

As an example in which a benzene ring of an aromatic hydrocarboncompound such as toluene is electrochemically hydrogenated, a method isreported, in which toluene that is vaporized into a gaseous state issent to the reduction electrode side to obtain methylcyclohexane, abenzene-ring hydrogenated substance (hydride), without going through astate of hydrogen gas in a configuration similar to that of waterelectrolysis (see Non-Patent Document 1); however, the amount ofsubstance that can be transformed per electrode area or time (currentdensity) is not large, and it has been difficult to industriallyhydrogenate a benzene ring of an aromatic hydrocarbon compound.

The present invention has been devised in view of these situations, anda purpose of the invention is to provide a technique in which at leastone benzene ring of an aromatic hydrocarbon compound or anitrogen-containing heterocyclic aromatic compound can be surely andelectrochemically hydrogenated at a high efficiency.

An aspect of the present invention is an electrochemical reductiondevice. The electrochemical reduction device comprises: an electrolytemembrane having ion conductivity; an electrode unit including both areduction electrode that is provided on one side of the electrolytemembrane and contains a reduction catalyst for hydrogenating at leastone benzene ring of an aromatic hydrocarbon compound or anitrogen-containing heterocyclic aromatic compound, and an oxygenevolving electrode provided on the other side of the electrolytemembrane; a power control unit that applies a voltage Va between thereduction electrode and the oxygen evolving electrode such that thereduction electrode has an electronegative potential and the oxygenevolving electrode has an electropositive potential; hydrogen gasgeneration amount measuring unit that measures a generation amount F1 ofhydrogen gas generated per unit time of an electrolysis reaction ofwater that competes with a hydrogenation reaction of at least onebenzene ring of the aromatic hydrocarbon compound or thenitrogen-containing heterocyclic aromatic compound; and a control unitthat releases, when the hydrogen gas generation amount F1 is larger thanan acceptable upper limit F0 of a hydrogen gas generation amount in theelectrode unit, the application of a voltage by the power control unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings that are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalfigures, in which:

FIG. 1 is a schematic view illustrating a schematic configuration of anelectrochemical reduction device according to Embodiment 1;

FIG. 2 is a view illustrating a schematic configuration of an electrodeunit included in the electrochemical reduction device according toEmbodiment 1;

FIG. 3 is a flowchart illustrating an example of potential control of areduction electrode by a control unit in Embodiment 1;

FIG. 4 is a schematic view illustrating a schematic configuration of anelectrochemical reduction device according to Embodiment 2; and

FIG. 5 is a view illustrating a specific example of a gas-liquidseparation unit.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

One embodiment of the present invention is an electrochemical reductiondevice. The electrochemical reduction device comprises: an electrolytemembrane having ion conductivity; an electrode unit including both areduction electrode that is provided on one side of the electrolytemembrane and contains a reduction catalyst for hydrogenating at leastone benzene ring of an aromatic hydrocarbon compound or anitrogen-containing heterocyclic aromatic compound, and an oxygenevolving electrode provided on the other side of the electrolytemembrane; a power control unit that applies a voltage Va between thereduction electrode and the oxygen evolving electrode such that thereduction electrode has an electronegative potential and the oxygenevolving electrode has an electropositive potential; hydrogen gasgeneration amount measuring unit that measures a generation amount F1 ofhydrogen gas generated per unit time of an electrolysis reaction ofwater that competes with a hydrogenation reaction of at least onebenzene ring of the aromatic hydrocarbon compound or thenitrogen-containing heterocyclic aromatic compound; and a control unitthat releases, when the hydrogen gas generation amount F1 is larger thanan acceptable upper limit F0 of a hydrogen gas generation amount in theelectrode unit, the application of a voltage by the power control unit.

The electrochemical reduction device of the aforementioned aspect mayfurther comprise: a reference electrode that is arranged to contact theelectrolyte membrane and to be electrically isolated from the reductionelectrode and the oxygen evolving electrode and that is held at areference electrode potential V_(Ref); and a voltage detection unit thatdetects a potential difference ΔV_(CA) between the reference electrodeand the reduction electrode, in which the control unit may measures apotential V_(CA) in the reduction electrode based on the potentialdifference ΔV_(CA) and the reference electrode potential V_(Ref).

Another embodiment of the present invention is an electrochemicalreduction device. The electrochemical reduction device comprises: anelectrolyte membrane having on conductivity; an electrode unit assemblyin which a plurality of electrode units are connected in series witheach other, the each electrode unit including both a reduction electrodethat is provided on one side of the electrolyte membrane and contains areduction catalyst for hydrogenating at least one benzene ring of anaromatic hydrocarbon compound or a nitrogen-containing heterocyclicaromatic compound, and an oxygen evolving electrode provided on theother side of the electrolyte membrane; a power control unit thatapplies a voltage Va between a positive electrode terminal and anegative electrode terminal of the electrode unit assembly such that thereduction electrode of the each electrode unit has an electronegativepotential and the oxygen evolving electrode thereof has anelectropositive potential; hydrogen gas generation amount measuringdevice that measures, in the whole electrode units, a generation amountF1′ of hydrogen gas generated per unit time of an electrolysis reactionof water that competes with a hydrogenation reaction of at least onebenzene ring of the aromatic hydrocarbon compound or thenitrogen-containing heterocyclic aromatic compound; and a control unitthat releases, when the hydrogen gas generation amount F1′ is largerthan an acceptable upper limit F0×N (wherein F0 represents an acceptableupper limit of a hydrogen gas generation amount per one of the electrodeunits, and N the number of the electrode units), the application of avoltage by the power control unit.

The electrochemical reduction device of the aforementioned aspect mayfurther comprise: a reference electrode that is arranged to contact theelectrolyte membrane of any one of the electrode units included in theelectrode unit assembly and to be electrically isolated from thereduction electrode and the oxygen evolving electrode of the electrodeunit; and a voltage detection unit that detects a potential differenceΔV_(CA) between the reference electrode and the reduction electrode ofthe electrode unit, in which the control unit may measure a potentialV_(CA) in the reduction electrode of the electrode unit based on thepotential difference ΔV_(CA) and the reference electrode potentialV_(Ret).

Another embodiment of the present invention is a method of manufacturinga hydride of an aromatic hydrocarbon compound or a nitrogen-containingheterocyclic aromatic compound. The method of manufacturing a hydride ofan aromatic hydrocarbon compound or a nitrogen-containing heterocyclicaromatic compound comprises: using the electrochemical reduction deviceof any one of the aforementioned aspects; introducing an aromatichydrocarbon compound or a nitrogen-containing heterocyclic aromaticcompound into the reduction electrode side of the electrode unit;circulating water or humidified gas to the oxygen evolving electrodeside; and producing a hydride of the aromatic hydrocarbon compound orthe nitrogen-containing heterocyclic aromatic compound introduced intothe reduction electrode side. In the manufacturing method of thisaspect, the aromatic hydrocarbon compound or the nitrogen-containingheterocyclic aromatic compound to be introduced into the reductionelectrode side may be introduced into the reduction electrode side in aliquid state at a reaction temperature.

Combinations of the aforementioned respective elements will also bewithin the scope of the present invention sought to be patented by thepresent patent application.

According to the present embodiment, at least one benzene ring of anaromatic hydrocarbon compound or a nitrogen-containing heterocyclicaromatic compound can be surely and electrochemically hydrogenated at ahigh efficiency.

Hereinafter, embodiments of the present invention will now be describedwith reference to the drawings. In the figures, like numerals representlike constituting elements and the description thereof will beappropriately omitted.

Embodiment 1

FIG. 1 is a schematic view illustrating a schematic configuration of anelectrochemical reduction device 10 according to an embodiment. FIG. 2is a view illustrating a schematic configuration of an electrode unit100 included in the electrochemical reduction device 10 according to theembodiment. As illustrated in FIG. 1, the electrochemical reductiondevice 10 comprises: an electrode unit 100, a power control unit 20, anorganic material storage tank 30, a hydrogen gas generation amountmeasuring unit 36, a water storage tank 40, a gas-water separation unit50, a gas-liquid separation unit 52, a control unit 60, and a hydrogengas recovery unit 210.

The power control unit 20 is, for example, a DC/DC converter forconverting the output voltage of a power source into a predeterminedvoltage. A positive electrode output terminal of the power control unit20 is connected to a positive electrode of the electrode unit 100. Anegative electrode output terminal of the power control unit 20 isconnected to a negative electrode of the electrode unit 100. Thereby, apredetermined voltage is applied between an oxygen evolving electrode(positive electrode) 130 and a reduction electrode (negative electrode)120 of the electrode unit 100. A reference electrode input terminal ofthe power control unit 20 is connected to a reference electrode 112provided on the later-described electrolyte membrane 110, and thepotentials in the positive electrode output terminal and the negativeelectrode output terminal are determined based on the potential in thereference electrode 112, in accordance with a command of the controlunit 60. As a power source, electrical power derived from natural energysuch as sunlight and wind power can be used. A mode in which thepotential control of the positive electrode output terminal and thenegative electrode output terminal by the control unit 60 will bedescribed later.

The organic material storage tank 30 stores an aromatic compound. Thearomatic compound used in the present embodiment is an aromatichydrocarbon compound or a nitrogen-containing heterocyclic aromaticcompound, which contains at least one aromatic ring, and examplesthereof include benzene, naphthalene, anthracene, diphenylethane,pyridine, pyrimidine, pyrazine, quinoline, isoquinoline, N-alkylpyrrole,N-alkylindole, N-alkyldibenzopyrrole, and the like. From one to fourhydrogen atoms of an aromatic ring of any one of the aforementionedaromatic hydrocarbon compounds or nitrogen-containing heterocyclicaromatic compounds may be substituted by alkyl groups. However, the“alkyl” of any one of the aromatic compounds is a C₁₋₆ straight orbranched alkyl group. For example, alkylbenzenes include toluene, ethylbenzene, and the like; dialkylbenzenes include xylene, diethylbenzene,and the like; and trialkylbenzenes include mesitylene and the like.Alkylnaphthalenes include methylnaphthalene and the like. An aromaticring of any one of the aromatic hydrocarbons or nitrogen-containingheterocyclic aromatic compounds may have from 1 to 3 substituents. Inthe following description, the aromatic hydrocarbon compound and thenitrogen-containing heterocyclic aromatic compound to be used in thepresent invention may be referred to as “aromatic compounds”. It ispreferable that the aromatic compound is a liquid at room temperature.When a mixture of two or more of the aforementioned aromatic compoundsis used, the mixture should be a liquid. Consequently, the aromaticcompound can be supplied to the electrode unit 100 in a liquid statewithout being heated, pressurized, or the like, and hence theconfiguration of the electrochemical reduction device 10 can besimplified. The concentration of the aromatic hydrocarbon compound in aliquid state is 0.1% or more, preferably 0.3% or more, and morepreferably 0.5% or more.

The aromatic compound stored in the organic material storage tank 30 issupplied to the reduction electrode 120 of the electrode unit 100 by afirst liquid supply device 32. As the first liquid supply device 32, forexample, various types of pumps such as a gear pump or a cylinder pump,or a gravity flow device or the like can be used. Instead of thearomatic compound, an N-substitution product of the aforementionedaromatic compound may be used. A circulation pathway is provided betweenthe organic material storage tank 30 and the reduction electrode of theelectrode unit 100, so that the aromatic compound, a hydride of whichhas been produced by the electrode unit 100, and an unreacted aromaticcompound are stored in the organic material storage tank 30 afterpassing through the circulation pathway. Although gas is not generatedin a main reaction that proceeds in the reduction electrode 120 of theelectrode unit 100, hydrogen is generated by an electrolysis reaction ofwater that competes with a hydrogenating reaction of at least onebenzene ring of an aromatic compound. In order to remove this hydrogen,the gas-liquid separation unit 52 is provided. The hydrogen gasseparated by the gas-liquid separation unit 52 is housed in the hydrogengas recovery unit 210. Also, the hydrogen gas generation amountmeasuring unit 36 is provided in piping 31 extending from the reductionelectrode 120 to the organic material storage tank 30 and in thepreceding stage of the gas-liquid separation unit 52. The hydrogen gasgeneration amount measuring unit 36 measures an amount of the hydrogengas circulating through the piping 31 along with an aromatic compound.As the hydrogen gas generation amount measuring unit 36, for example, anoptical sensor for optically detecting bubbles generated by the hydrogengas, a pressure sensor for detecting the pressure in the piping 31, orthe like, can be used. Information on the hydrogen gas generationamount, measured by the hydrogen gas generation amount measuring unit36, is inputted to the control unit 60, so that a hydrogen gasgeneration amount F1 is calculated based on the information.

The water storage tank 40 stores ion-exchanged water, purified water, orthe like (hereinafter, simply referred to as “water”). The water storedin the water storage tank 40 is supplied to the oxygen evolvingelectrode 130 of the electrode unit 100 by a second liquid supply device42. As the second liquid supply device 42, for example, various types ofpumps such as a gear pump or a cylinder pump, or a gravity flow deviceor the like can be used, similarly to the first liquid supply device 32.A circulation pathway is provided between the water storage tank 40 andthe oxygen evolving electrode of the electrode unit 100, and the waterthat is unreacted in the electrode unit 100 is stored in the waterstorage tank 40 after passing through the circulation pathway. Thegas-water separation unit 50 is provided in the middle of a pathwaywhere the unreacted water is sent back to the water storage tank 40 fromthe electrode unit 100. By the gas-water separation unit 50, the oxygengenerated by the electrolysis of water in the electrode unit 100 isseparated from water and discharged to the outside the system.

As illustrated in FIG. 2, the electrode unit 100 includes theelectrolyte membrane 110, the reduction electrode 120, the oxygenevolving electrode 130, liquid diffusion layers 140 a and 140 b, andseparators 150 a and 150 b. In FIG. 1, the electrode unit 100 isillustrated in a simplified way in which the liquid diffusion layers 140a and 140 b and the separators 150 a and 150 b are omitted.

The electrolyte membrane 110 is formed of a material (ionomer) havingprotonic conductivity, and inhibits substances from getting mixed orbeing diffused between the reduction electrode 120 and the oxygenevolving electrode 130 while selectively conducting protons. Thethickness of the electrolyte membrane 110 is preferably from 5 to 300μm, more preferably from 10 to 150 μm, and most preferably from 20 to100 μm. If the thickness of the electrolyte membrane 110 is less than 5μm, the barrier property of the electrolyte membrane 110 isdeteriorated, so that cross-leaking is likely to occur. On the otherhand, if the thickness thereof is more than 300 μm, ion transferresistance becomes too large, which is not preferred.

The area resistance of the electrolyte membrane 110, that is, the iontransfer resistance per geometric area thereof is preferably 2000 mΩ*cm²or less, more preferably 1000 mΩ*cm² or less, and most preferably 500mΩ*cm² or less. If the area resistance of the electrolyte membrane 110is more than 2000 mΩ*cm², protonic conductivity becomes insufficient.Examples of the material having protonic conductivity (i.e., acation-exchanging ionomer) include perfluorosulfonic acid polymers suchas Nafion (registered trademark) and Flemion (registered trademark). Theion exchange capacity (IEC) of the cation exchange ionomer is preferablyfrom 0.7 to 2 meq/g, and more preferably from 1 to 1.2 meq/g. If the ionexchange capacity thereof is less than 0.7 meq/g, ion conductivitybecomes insufficient. On the other hand, if the ion exchange capacity ofthe cation exchange ionomer is more than 2 meq/g, the solubility of theionomer in water is increased, and hence the strength of the electrolytemembrane 110 becomes insufficient.

On the electrolyte membrane 110, the reference electrode 112 is providedin an area spaced apart from the reduction electrode 120 and the oxygenevolving electrode 130 so as to contact the electrolyte membrane 110.That is, the reference electrode 112 is electrically isolated from thereduction electrode 120 and the oxygen evolving electrode 130. Thereference electrode 112 is held at a reference electrode potentialV_(Ref). Examples of the reference electrode 112 include a standardhydrogen reduction electrode (reference electrode potential V_(Ref)=0 V)and an Ag/AgCl electrode (reference electrode potential V_(ref)=0.199V), but the reference electrode 112 is not limited thereto. Thereference electrode 112 is preferably provided on the surface of theelectrolyte membrane 110 on the reduction electrode 120 side.

A potential difference ΔV_(CA) between the reference electrode 112 andthe reduction electrode 120 is detected by a voltage detection unit 114.The value of the potential difference ΔV_(CA) detected by the voltagedetection unit 114 is inputted to the control unit 60.

The reduction electrode 120 is provided on one side of the electrolytemembrane 110. The reduction electrode 120 is a reduction electrodecatalyst layer containing a reduction catalyst for producing a hydrideof an aromatic compound. The reduction catalyst to be used in thereduction electrode 120 is not particularly limited, and is made, forexample, of a metal composition that includes a first catalyst metal(noble metal) containing at least one of Pt and Pd, and one or moresecond catalyst metals selected from the group consisting of Cr, Mn, Fe,Co, Ni, Cu, Zn, Mo, Ru, Sn, W, Re, Pb, and Bi. The form of the metalcomposition is an alloy of the first catalyst metal and the secondcatalyst metals, or an intermetallic compound composed of the firstcatalyst metal and the second catalyst metals. The ratio of the firstcatalyst metal to the total mass of the first catalyst metal and thesecond catalyst metals is preferably from 10 to 95 wt %, more preferablyfrom 20 to 90 wt %, and most preferably from 25 to 80 wt %. If the ratioof the first catalyst metal is less than 10 wt %, durability may bedeteriorated in terms of resistance to dissolving, and the like. On theother hand, if the ratio of the first catalyst metal is more than 95 wt%, the properties of the reduction catalyst become closer to those of anoble metal alone, and hence the electrode activity becomesinsufficient. In the following description, the first catalyst metal andthe second catalyst metals may be collectively referred to as a“catalyst metal.”

The aforementioned catalyst metal may be supported by a conductivematerial (support). The electrical conductivity of the conductivematerial is preferably 1.0×10⁻² S/cm or more, more preferably 3.0×10⁻²S/cm or more, and most preferably 1.0×10⁻¹ S/cm or more. If theelectrical conductivity of the conductive material is less than 1.0×10⁻²S/cm, sufficient conductivity cannot be imparted. Examples of theconductive material include conductive materials containing any one of aporous carbon, a porous metal, and a porous metal oxide as a majorcomponent. Examples of the porous carbon include carbon black such asKetjen black (registered trademark), acetylene black, and Vulcan(registered trademark). The BET specific surface area of the porouscarbon measured by a nitrogen adsorption method is preferably 100 m²/gor more, more preferably 150 m²/g or more, and most preferably 200 m²/qor more. If the BET specific surface area of the porous carbon is lessthan 100 m²/g, it is difficult to uniformly support the catalyst metals.Accordingly, the rate of utilizing the surface of the catalyst metal isdecreased, causing the catalyst performance to be deteriorated. Examplesof the porous metal include, for example, Pt black, Pd black, a Pt metaldeposited in a fractal shape, and the like. Examples of the porous metaloxide include oxides of Ti, Zr, Nb, Mo, Hf, Ta and W. Besides these,examples of the porous conductive material for supporting the catalystmetal include nitrides, carbides, oxynitrides, carbonitrides,partially-oxidized carbonitrides of metals such as Ti, Zr, Nb, Mo, Hf,Ta, and W (hereinafter, they are collectively referred to as porousmetal carbonitrides and the like). The BET specific surface areas of theporous metal, the porous metal oxide, the porous metal carbonitrides andthe like measured by a nitrogen adsorption method are preferably 1 m²/gor more, more preferably 3 m²/g or more, and most preferably 10 m²/g ormore. If the respective BET specific surface areas of the porous metal,the porous metal oxide, the porous metal carbonitrides and the like areless than 1 m²/g, it is difficult to uniformly support the catalystmetals. Accordingly, the rate of utilizing the surface of the catalystmetal is decreased, causing the catalyst performance to be deteriorated.

Depending on the types and compositions of the first catalyst metal andthe second catalyst metals, a simultaneous impregnation method, in whichthe first catalyst metal and the second catalyst metals aresimultaneously impregnated with a support, or a sequential impregnationmethod, in which, after the first catalyst metal is impregnated with asupport, the second catalyst metals are impregnated therewith, can beemployed as a method for supporting the catalyst metal on the support.In the case of the sequential impregnation method, after the firstcatalyst metal is supported on a support, a heat treatment or the likemay be performed once, followed by supporting the second catalyst metalson the support. After the impregnation of both the first catalyst metaland the second catalyst metals is completed, the first catalyst metaland the second catalyst metals are alloyed with each other or anintermetallic compound composed of the first catalyst metal and thesecond catalyst metals is formed by a heat treatment process.

To the reduction electrode 120, a material having conductivity, such asthe aforementioned conductive oxide or carbon black, may be addedseparately from the conductive compound for supporting the catalystmetal. Consequently, the number of electron-conducting paths amongreduction catalyst particles can be increased, and hence the resistanceper geometric area of a reduction catalyst layer can be lowered in somecases.

The reduction electrode 120 may include, as an additive, afluorine-based resin such as polytetrafluoroethylene (PTFE).

The reduction electrode 120 may contain an ionomer having protonicconductivity. The reduction electrode 120 preferably contains, at apredetermined mass ratio, an ionically conducting material (ionomer)having a structure that is identical or similar to that of theaforementioned electrolyte membrane 110. Thereby, the ion conductivityof the reduction electrode 120 can be improved. In particular, in thecase where a catalyst support is porous, the reduction electrode 120makes a significant contribution to the improvement of the ionconductivity by containing an ionomer that has protonic conductivity.Examples of the ionomer having protonic conductivity (i.e., acation-exchanging ionomer) include perfluorosulfonic acid polymers suchas Nafion (registered trademark) and Flemion (registered trademark). Theion exchange capacity (IEC) of the cation exchange ionomer is preferablyfrom 0.7 to 3 meq/g, more preferably from 1 to 2.5 meq/g, and mostpreferably from 1.2 to 2 meq/g. When the catalyst metal is supported onporous carbon (carbon support), a mass ratio I/C of thecation-exchanging ionomer (I) to the carbon support (C) is preferablyfrom 0.1 to 2, more preferably from 0.2 to 1.5, and most preferably from0.3 to 1.1. If the mass ratio I/C is less than 0.1, it is difficult toobtain sufficient ion conductivity. On the other hand, if the mass ratioI/C is more than 2, the thickness of an ionomer coating over thecatalyst metal is increased, and hence the contact of the aromaticcompound, a reactant, with a catalyst-active site may be inhibited orthe electrode activity may be decreased due to a decrease in theelectron conductivity.

It is also preferable that the reduction catalyst is partially coatedwith the ionomer included in the reduction electrode 120. Thereby, threeelements (aromatic compound, proton, electron), which are necessary foran electrochemical reaction in the reduction electrode 120, can beefficiently supplied to a reaction sites.

The liquid diffusion layer 140 a is laminated on the surface of thereduction electrode 120 on the side opposite to the electrolyte membrane110. The liquid diffusion layer 140 a has a function of uniformlydiffusing the liquid aromatic compound supplied from the later-describedseparator 150 a to the reduction electrode 120. As the liquid diffusionlayer 140 a, for example, carbon paper or carbon cloth is used.

The separator 150 a is laminated on the surface of the liquid diffusionlayer 140 a on the side opposite to the electrolyte membrane 110. Theseparator 150 a is formed of a carbon resin, or a corrosion-resistantalloy such as Cr—Ni—Fe, Cr—Ni—Mo—Fe, Cr—Mo—Nb—Ni, or Cr—Mo—Fe—W—Ni. Oneor more groove-like flow channels 152 a are provided on the surface ofthe separator 150 a on the liquid diffusion layer 140 a side. The liquidaromatic compound supplied from the organic substance storage tank 30circulates through the flow channel 152 a, and the liquid aromaticcompound penetrates into the liquid diffusion layer 140 a from the flowchannel 152 a. The form of the flow channel 152 a is not particularlylimited, but for example, a straight flow channel or a serpentine flowchannel can be employed. When a metal material is used for the separator150 a, the separator 150 a may have a structure formed by sinteringsphere-like or pellet-like metal fine powders.

The oxygen evolving electrode 130 is provided on the other side of theelectrolyte membrane 110. For the oxygen evolving electrode 130, amaterial, including a catalyst based on a noble metal oxide such as Ru₂or IrO₂, is preferably used. These catalysts may be supported in adispersed manner or coated on a metal substrate such as a metal wire ormesh made of metals such as Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ta, andW or of alloys composed primarily of these metals. In particular, whenIrO₂ is used as a catalyst, manufacturing costs can be reduced bycoating the metal substrate with a thin film because IrO₂ is expensive.

The liquid diffusion layer 140 b is laminated on the surface of theoxygen evolving electrode 130 on the side opposite to the electrolytemembrane 110. The liquid diffusion layer 140 b has a function ofuniformly diffusing the water supplied from the later-describedseparator 150 b to the oxygen evolving electrode 130. As the liquiddiffusion layer 140 b, for example, carbon paper or carbon cloth isused.

The separator 150 b is laminated on the surface of the liquid diffusionlayer 140 b on the side opposite to the electrolyte membrane 110. Theseparator 150 b is formed of a corrosion-resistant alloy such asCr/Ni/Fe, Cr/Ni/Mo/Fe, Cr/Mo/Nb/Ni, or Cr/Mo/Fe/W/Ni, or a material inwhich the surfaces of these metals are coated with an oxide layer. Oneor more groove-like flow channels 152 b are provided on the surface ofthe separator 150 b on the liquid diffusion layer 140 b side. The watersupplied from the water storage tank 40 circulates through the flowchannel 152 b, and the water penetrates into the liquid diffusion layer140 b from the flow channel 152 b. The form of the flow channel 152 b isnot particularly limited, but for example, a straight flow channel or aserpentine flow channel can be employed. When a metal material is usedfor the separator 150 b, the separator 150 b may have a structure formedby sintering sphere-like or pellet-like metal fine powders.

In the present embodiment, liquid water is supplied to the oxygenevolving electrode 130, but a humidified gas (for example, air) may beused instead of liquid water. In this case, the dew-point temperature ofthe humidified gas is preferably from room temperature to 100° C., andmore preferably from 50 to 100° C.

When toluene is used as the aromatic compound, reactions in theelectrode unit 100 are as follows.

<Electrode Reaction at Oxygen Evolving Electrode>

3H₂O→1.50₂+6H⁺+6e ⁻:E₀=1.23 V

<Electrode Reaction at Reduction Electrode>

Toluene+6H⁺+6e⁻→methylcyclohexane:E₀=0.153 V (vs RHE)

In other words, the electrode reaction at the oxygen evolving electrodeand that at the reduction electrode proceed in parallel, and protonsgenerated by electrolysis of water occurring due to the electrodereaction at the oxygen evolving electrode is supplied to the reductionelectrode via the electrolyte membrane 110, and used for producing ahydride of an aromatic compound in the electrode reaction at thereduction electrode.

Referring back to FIG. 1, the control unit 60 controls the power controlunit 20 so as to satisfy the relationship of V_(HER)−20mV→V_(CA)≦V_(TRR) (wherein V_(HER) represents the potential in areversible hydrogen electrode, and V_(CA) represents the potential inthe reduction electrode 120). If the potential V_(CA) is lower thanV_(HER)−20 mV, the hydrogenating (hydrogenating at least one benzenering of aromatic compound) reaction becomes to compete with a hydrogengeneration reaction, and hence the reduction selectivity of the aromaticcompound becomes insufficient, which is not preferred. On the otherhand, if the potential V_(CA) is higher than the standard redoxpotential V_(TRR), the hydride-producing reaction does not proceed at apractically sufficient rate, which is not preferred. In other words, bysetting the potential V_(CA) to be within the range that satisfies theaforementioned relational expression, electrochemical reactions can bemade to proceed at both the electrodes, and the hydrogenating at leastone benzene ring of the aromatic compound can be industrially practiced.

After the potential V_(CA) is adjusted, the control unit 60 executes theprocessing for stopping electrode reactions at the reduction electrode120 and the oxygen evolving electrode 130, when the hydrogen gasgeneration amount F1, measured by the hydrogen gas generation amountmeasuring unit 36, is larger than F0. Specifically, examples of theprocessing to be executed by the control unit 60 when F1 is larger thanF0 include the processing for causing the voltage Va to be 0instantaneously or in a stepwise fashion, or the processing for blockingthe power supply from a power source to the power control unit 20 byproviding an isolating switch in a power source line extending from thepower source to the power control unit 20, and the like. Thus, byterminating the electrode reactions in a state where the hydrogen gasgeneration amount F1 is larger than the acceptable upper limit F0, thatis, in a state where the Faraday efficiency is decreased, the Faradayefficiency can be maintained to be larger than or equal to apredetermined value while the electrode reactions are proceeding.

When the total current density flowing through the electrode unit 100 isrepresented by a current density A, and a current density used in thereduction of the aromatic compound, the current density beingback-calculated from the generation amount of a hydride of the aromaticcompound that has been quantitated by gas chromatography, etc., isrepresented by a current density B, the Faraday efficiency is calculatedby the current density B/ the current density A×100(%).

Besides this, the following reaction conditions are employed for theproduction of a hydride of the aromatic compound using theelectrochemical reduction device 10. The temperature of the electrodeunit 100 is preferably from room temperature to 100° C., and morepreferably from 40 to 80° C. If the temperature of the electrode unit100 is lower than room temperature, the proceeding of the electrolyticreaction may be slowed down, or an enormous amount of energy is requiredto remove the heat generated as the main reaction proceeds, which is notpreferred. On the other hand, if the temperature of the electrode unit100 is higher than 100° C., water is brought to a boil at the oxygenevolving electrode 130 and the vapor pressure of an organic material isincreased at the reduction electrode 120, which is not preferred for theelectrochemical reduction device 10 in which reactions are performed inliquid phases at both the electrodes.

FIG. 3 is a flowchart illustrating an example of the potential controlof the reduction electrode 120 performed by the control unit 60 of thepresent embodiment. The mode of performing the potential control of thereduction electrode 120 will be described below by using, as an example,a case where an Ag/AgCl electrode (reference electrode potentialV_(Ref)=0.199 V) is used as the reference electrode 112.

The potential V_(CA) (target value), which satisfies V_(HER)−anacceptable potential difference≦V_(CA)≦V_(TRR), is first set (S10). Theacceptable potential difference may be 20 mV. In an aspect, thepotential V_(CA) (target value) is a value that has been storedbeforehand in a memory such as a ROM. In another aspect, the potentialV_(CA) (target value) is set by a user.

Subsequently, a voltage detection unit 114 detects a potentialdifference ΔV_(CA) between the reference electrode 112 and the reductionelectrode 120 (S20).

Subsequently, the control unit 60 calculates a potential V_(CA)(actually measured value) in the reduction electrode 120 by using(expression) V_(CA)=ΔV_(CA)−V_(Ref)=ΔV_(CA)−0.199 V (S30).

Subsequently, it is determined whether the potential V_(CA) (actuallymeasured value) satisfies the following expressions (1) and (2) (S40).

|Potential V _(CA) (actually measured value)−Potential V _(CA) (targetvalue)|≦Acceptable Value  (1)

V _(HER)−Acceptable Potential Difference≦V _(CA) (actually measuredvalue)≦_(TRR)  (2)

In the expression (1), the acceptable value is, for example, 1 mV.

When the potential V_(CA) (actually measured value) satisfies theexpressions (1) and (2), the processing proceeds to “yes” in S40 so asto proceed to the later-described S60. On the other hand, when thepotential V_(CA) (actually measured value) does not satisfy both theexpressions (1) and (2), the processing proceeds to “No” in S40 so as toadjust the voltage Va to be applied between the reduction electrode 120and the oxygen evolving electrode 130 (S50). After the adjustment of thevoltage Va, the processing returns to the aforementioned S10.

Herein, an example of the adjustment of the voltage Va will bedescribed. For example, when Potential V_(CA) (actually measuredvalue)−Potential V_(CA) (target value)>Acceptable Value, the controlunit 60 sends to the power control unit 20 a command requesting that thevoltage Va is increased by only 1 mV. As a result of increasing thevoltage Va, if V_(GA) (actually measured value)<V_(HER)−AcceptablePotential Difference even when Potential V_(CA) (actually measuredvalue)−Potential V_(CA) (target value)|≦Acceptable Value is satisfied,the expression (2) is not satisfied, and hence the control unit 60causes the voltage Va to be further decreased by 1 mV in the nextprocessing. Thus, the control unit 60 causes the voltage Va to bedecreased in a stepwise fashion until the expressions (1) and (2) arefinally satisfied.

On the other hand, when Potential V_(CA) (actually measuredvalue)−Potential V_(CA) (target value)<−Acceptable Value, the controlunit 60 sends to the power control unit 20 a command requesting that thevoltage Va is decreased by only 1 mV. As a result of decreasing thevoltage Va, if V_(CA) (actually measured value)>V_(TRR) even when|Potential V_(CA) (actually measured value)−Potential V_(CA) (targetvalue)|≦Acceptable Value is satisfied, the expression (2) is notsatisfied, and hence the control unit 60 causes the voltage Va to befurther increased by 1 mV in the next processing. Thus, the control unit60 causes the voltage Va to be increased in a stepwise fashion until theexpressions (1) and (2) are finally satisfied.

Herein, the value (adjustment range) by which the voltage Va isincreased or decreased is not limited to 1 mV. For example, it may beacceptable that the adjustment range of the voltage Va is set to becomparable to the aforementioned acceptable value in the first round ofthe adjustment of the voltage Va and the adjustment range thereof is setto, for example, one-fourth of the aforementioned acceptable value inthe second and subsequent rounds of the adjustment of the voltage Va.Thereby, the potential V_(CA) (actually measured value) can be quicklyadjusted to be within a range that satisfies the expressions (1) and(2).

After the voltage Va is adjusted in S50 or in the case of “yes” in S40,the hydrogen gas generation amount F1 is measured by the hydrogen gasgeneration amount measuring unit 36 (S60).

Subsequently, it is determined whether the hydrogen gas generationamount F1 is smaller than or equal to the acceptable upper limit F0(S70). When the hydrogen gas generation amount F1 is smaller than orequal to the acceptable upper limit F0, the processing proceeds to “yes”in S70 so as to detect the potential difference ΔV_(CA) again (S20). Onthe other hand, when the hydrogen gas generation amount F1 is largerthan the acceptable upper limit F0, the processing proceeds to “No” inS70 so as to stop the electrode reactions at the reduction electrode 120and the oxygen evolving electrode 130.

Embodiment 2

FIG. 4 is a schematic view illustrating a schematic configuration of anelectrochemical reduction device 10 according to Embodiment 2. Asillustrated in FIG. 4, the electrochemical reduction device 10comprises: an electrode unit assembly 200, a power control unit 20, anorganic material storage tank 30, a hydrogen gas generation amountmeasuring unit 36, a water storage tank 40, a gas-water separation unit50, a gas-liquid separation unit 52, a control unit 60, a voltagedetection unit 114, and a hydrogen gas recovery unit 210. The electrodeunit assembly 200 has a laminate structure in which a plurality ofelectrode units 100 are connected in series with each other. In thepresent embodiment, the number of the electrode units 100 is 5; however,the number thereof is not limited thereto. Herein, each electrode unit100 has the same configuration as that in Embodiment 1. In FIG. 4, theelectrode unit 100 is illustrated in a simplified way in which liquiddiffusion layers 140 a and 140 b and separators 150 a and 150 b areomitted.

A positive electrode output terminal of the power control unit 20according to the present embodiment is connected to positive electrodesof the electrode unit assembly 200. On the other hand, a negativeelectrode output terminal of the power control unit 20 is connected tonegative electrodes of the electrode unit assembly 200. Thereby, apredetermined voltage Va is applied between the positive electrodeterminals and the negative electrode terminals of the electrode unitassembly 200, so that in each electrode units 100, a reduction electrode120 has an electronegative potential and an oxygen evolving electrode130 has an electropositive potential. Herein, a reference electrodeinput terminal of the power control unit 20 is connected to a referenceelectrode 112 provided on an electrolyte membrane 110 of thelater-described specific electrode unit 100, so that the potentials inthe positive electrode output terminal and the negative electrode outputterminal are determined based on the potential in the referenceelectrode 112.

A first circulation pathway is provided between the organic materialstorage tank 30 and the reduction electrode 120 of each electrode unit100. An aromatic compound stored in the organic material storage tank 30is supplied to the reduction electrode 120 of each electrode unit 100 bya first liquid supply device 32. Specifically, the piping that forms thefirst circulation pathway is branched on the downstream side of thefirst liquid supply device 32, so that the aromatic compound isdistributed and supplied to the reduction electrode 120 of eachelectrode unit 100. The aromatic compound, a hydride of which has beenproduced by each electrode unit 100, and an unreacted aromatic compoundjoin together in the piping 31 communicating to the organic materialstorage tank 30, so that they are stored therein after passing throughthe piping 31. The gas-liquid separation unit 52 is provided in themiddle of the piping 31, so that the hydrogen, circulating the inside ofthe piping 31, is separated by the gas-liquid separation unit 52.

FIG. 5 is a view illustrating a specific example of the gas-liquidseparation unit 52. A branch pipe 33, branching upwards from the piping31, is provided. The branch pipe 33 is connected to the bottom of aliquid storage tank 35. A liquefied aromatic compound flows into theliquid storage tank 35 via the branch pipe 33, so that the liquid levelin the liquid storage tank 35 is maintained at a predetermined level.The hydrogen gas, flowing through the piping 31 from the upstream sideof the point where the branch pipe 33 is branched to the branch pointalong with the aromatic compound, reaches the liquid storage tank 35after moving upwards through the branch pipe 33, and enters the gasphase above the liquid level in the liquid storage tank 35. The hydrogengas in the gas phase is then recovered by the hydrogen gas recovery unit210 via an exhaust pipe 37 connected to the upper portion of the liquidstorage tank 35. The hydrogen gas generation amount measuring unit 36 isprovided in the middle of the exhaust pipe 37 such that the hydrogen gasgeneration amount F1′, generated from all the electrode units 100included in the electrode unit assembly 200, is measured. In the presentembodiment, the hydrogen gas generation amount measuring unit 36 is aflowmeter for detecting the amount of the hydrogen gas passing throughthe exhaust pipe 37. Herein, a constant amount of nitrogen gas may besupplied to the exhaust pipe 37 at the upstream of the hydrogen gasgeneration amount measuring unit 36. Thereby, a change in theconcentration of the hydrogen gas flowing through the exhaust pipe 37can be accurately detected.

In the aforementioned embodiment, a flowmeter is adopted as an exampleof the hydrogen gas generation amount measuring unit 36; however, thehydrogen gas generation amount measuring unit 36 is not limited thereto.For example, a mode can be adopted, in which a relief valve is installedin the exhaust pipe 37 as the hydrogen gas generation amount measuringunit 36. The relief valve is configured, for example, to open when thegas pressure in the exhaust pipe 37 on the upstream side thereof becomeslarger than or equal to a preset value, and to close after a constantamount of the gas is discharged toward the downstream side of the reliefvalve. In this case, a signal, indicating that the relief valve isopened, is transmitted to the control unit 60 every time the reliefvalve is opened. The control unit 60 estimates a hydrogen gas generationamount based on both the amount of the gas discharged per one opening ofthe relief valve and the number of the openings of the relief valve perunit time.

In the present embodiment, the flow rate of the hydrogen gas separatedby the gas-liquid separation unit 52 is measured by the hydrogen gasgeneration amount measuring unit 36; however, an optical sensor, similarto that in Embodiment 1, may be installed between the upstream side ofthe gas-liquid separation unit 52 and the downstream side of the pointwhere the piping from the respective electrode units 100 join together.In addition, in Embodiment 1, a mode may be adopted as in Embodiment 3,in which the flow rate of the hydrogen gas separated by the gas-liquidseparation unit 52 is measured by the hydrogen gas generation amountmeasuring unit 36.

A second circulation pathway is provided between the water storage tank40 and the oxygen evolving electrode 130 of each electrode unit 100. Thewater stored in the water storage tank 40 is supplied to the oxygenevolving electrode 130 of each electrode unit 100 by the second liquidsupply device 42. Specifically, piping that forms the second circulationpathway is branched on the downstream side of the second liquid supplydevice 42, so that water is distributed and supplied to the oxygenevolving electrode 130 of each electrode unit 100. The unreacted waterin each electrode unit 100 joins together in the piping thatcommunicates to the water storage tank 40, and then is stored in thewater storage Lank 40 after passing through the piping.

Alike Embodiment 1, a reference electrode 112 is provided on theelectrolyte membrane 110 of a specific electrode unit 100 so as tocontact the electrolyte membrane 110 in an area spaced apart from thereduction electrode 120 and the oxygen evolving electrode 130. Thespecific electrode unit 100 may be any one of the plurality of theelectrode units 100.

A potential difference ΔV_(CA) between the reference electrode 112 andthe reduction electrode 120 is detected by the voltage detection unit114. The value of the potential difference ΔV_(CA) detected by thevoltage detection unit 114 is inputted to the control unit 60.

When the potential in a reversible hydrogen electrode is represented byV_(HER), the potential in the reduction electrode 120 by V_(CA), anacceptable upper limit of the hydrogen gas generation amount per oneelectrode unit by F0, and the number of the electrode units 100 by N (inthe present embodiment, N is 5), the control unit 60 controls the powercontrol unit 20 so as to gradually increase the voltage Va within arange of F1′≦N×F0 and V_(CA)>V_(HER)−Acceptable Potential Difference.

On the other hand, when F1′ is larger than N×F0, the control unit 60executes the processing for stopping the electrode reactions at thereduction electrode 120 and the oxygen evolving electrode 130.Specifically, examples of the processing to be executed by the controlunit 60 when F1′ is larger than N×F0 include the processing for causingthe voltage Va to be 0 instantaneously or in a stepwise fashion, or theprocessing for blocking the power supply from a power source to thepower control unit 20 by providing an isolating switch in a power sourceline extending from the power source to the power control unit 20, andthe like. Thus, by terminating the electrode reactions in a state wherethe hydrogen gas generation amount F1′ is larger than the acceptableupper limit N×F0, that is, in a state where the Faraday efficiency isdecreased, the Faraday efficiency can be maintained to be larger than orequal to a predetermined value while the electrode reactions areproceeding in each electrode unit 100.

According to the present embodiment, the production of hydrides of anaromatic compound can be made to proceed in parallel in a plurality ofthe electrode units 100, and hence the generation amount of a hydride ofan aromatic compound per unit time can be drastically increased.Accordingly, the production of a hydride of an aromatic compound can beindustrially practiced.

The present invention is not limited to the aforementioned embodiments,and various modifications, such as a design change, can be added theretobased on knowledge of those skilled in the art, and any embodiment towhich such modifications are added can also be included in the scope ofthe present invention.

In the aforementioned embodiments, the mode, in which the electrolytemembrane 110 and the reduction electrode 120 contain ionomers havingprotonic conductivity, has been described as an example, but they maycontain ionomers having hydroxy ion conductivity.

In Embodiment 2, the reference electrode 112 is installed on theelectrolyte membrane 110 in one electrode unit 100, but the referenceelectrode 112 may be installed on the electrolyte membranes 110 of aplurality of the electrode units 100. In this case, the potentialdifference ΔV_(CA) between the reference electrode 112 and thecorresponding reduction electrode 120 is detected by the voltagedetection unit 114, so that the voltage V_(CA) is calculated by usingthe average of the detected multiple potential differences ΔV_(CA).Thereby, the voltage Va can be adjusted to be within a more appropriaterange, when a variation in the potentials is caused among the electrodeunits 100.

1. An electrochemical reduction device comprising: an electrolytemembrane having ion conductivity; an electrode unit including both areduction electrode that is provided on one side of the electrolytemembrane and contains a reduction catalyst for hydrogenating at leastone benzene ring of an aromatic hydrocarbon compound or anitrogen-containing heterocyclic aromatic compound, and an oxygenevolving electrode provided on the other side of the electrolytemembrane; a power control unit that applies a voltage Va between thereduction electrode and the oxygen evolving electrode such that thereduction electrode has an electronegative potential and the oxygenevolving electrode has an electropositive potential; hydrogen gasgeneration amount measuring unit that measures a generation amount F1 ofhydrogen gas generated per unit time of an electrolysis reaction ofwater that competes with a hydrogenation reaction of at least onebenzene ring of the aromatic hydrocarbon compound or thenitrogen-containing heterocyclic aromatic compound; and a control unitthat releases, when the hydrogen gas generation amount F1 is larger thanan acceptable upper limit F0 of a hydrogen gas generation amount in theelectrode unit, the application of a voltage by the power control unit.2. The electrochemical reduction device according to claim 1 furthercomprising: a reference electrode that is arranged to contact theelectrolyte membrane and to be electrically isolated from the reductionelectrode and the oxygen evolving electrode and that is held at areference electrode potential V_(Ref); and a voltage detection unit thatdetects a potential difference ΔV_(CA) between the reference electrodeand the reduction electrode, wherein the control unit measures apotential V_(CA) in the reduction electrode based on the potentialdifference ΔV_(CA) and the reference electrode potential V_(Ref).
 3. Anelectrochemical reduction device comprising: an electrolyte membranehaving ion conductivity; an electrode unit assembly in which a pluralityof electrode units are connected in series with each other, the eachelectrode unit including both a reduction electrode that is provided onone side of the electrolyte membrane and contains a reduction catalystfor hydrogenating at least one benzene ring of an aromatic hydrocarboncompound or a nitrogen-containing heterocyclic aromatic compound, and anoxygen evolving electrode provided on the other side of the electrolytemembrane; a power control unit that applies a voltage Va between apositive electrode terminal and a negative electrode terminal of theelectrode unit assembly such that the reduction electrode of the eachelectrode unit has an electronegative potential and an oxygen evolvingelectrode thereof has an electropositive potential; hydrogen gasgeneration amount measuring unit that measures, in the whole electrodeunits, a generation amount F1′ of hydrogen gas generated per unit timeof an electrolysis reaction of water that competes with a hydrogenationreaction of at least one benzene ring of the aromatic hydrocarboncompound or the nitrogen-containing heterocyclic aromatic compound; anda control unit that releases, when the hydrogen gas generation amountF1′ is larger than an acceptable upper limit F0×N (wherein F0 representsan acceptable upper limit of a hydrogen gas generation amount per one ofthe electrode units, and N the number of the electrode units), theapplication of a voltage by the power control unit.
 4. Theelectrochemical reduction device according to claim 3 furthercomprising: a reference electrode that is arranged to contact theelectrolyte membrane of any one of the electrode units included in theelectrode unit assembly and to be electrically isolated from thereduction electrode and the oxygen evolving electrode of the electrodeunit; and a voltage detection unit that detects a potential differenceΔV_(CA) between the reference electrode and the reduction electrode ofthe electrode unit, wherein the control unit measures a potential V_(CA)in the reduction electrode of the electrode unit based on the potentialdifference ΔV_(CA) and the reference electrode potential V_(Ref).
 5. Amethod of manufacturing a hydride of an aromatic hydrocarbon compound ora nitrogen-containing heterocyclic aromatic compound, comprising: usingthe electrochemical reduction device of claim 1; introducing an aromatichydrocarbon compound or a nitrogen-containing heterocyclic aromaticcompound into the reduction electrode side of the electrode unit;circulating water or humidified gas to the oxygen evolving electrodeside; and producing a hydride of the aromatic hydrocarbon compound orthe nitrogen-containing heterocyclic aromatic compound introduced intothe reduction electrode side.
 6. The method of manufacturing a hydrideof an aromatic hydrocarbon compound or a nitrogen-containingheterocyclic aromatic compound according to claim 5, wherein thearomatic compound or the nitrogen-containing heterocyclic aromaticcompound to be introduced into the reduction electrode side isintroduced into the reduction electrode side in a liquid state at areaction temperature.